This invention relates to motor drive units, and more particularly to camera motor drive units with photographic cameras wherein the drive control circuit for an electric motor is provided with braking means.
It is known to supply a drive control circuit for a film winding electric motor with a brake transistor that short-circuits the motor winding when the motor is to be stopped. Such conventional motor drive control circuit, however, require the use of a diode such as diode D connected, as shown in FIG. 1, between an energy supply control switch S and the winding of the motor M all of them are connected in series with the source of energy or battery E. The dopde D is arranged between the base and emitter electrodes of the brake transistor Tr. When switch S is opened at the termination of a film feeding stroke to deenergize the motor M, the brake transistor Tr is rendered conductive momentarily by by virtue of a base current supplied as an induction voltage produced in the winding of the motor, while nevertheless preventing the direct application of the induction voltage to the base of brake transistor Tr. Hence the tendency of the motor to travel past the end of a feeding stroke is minimized in this way. This arrangement of the diode D gives rise to the disadvantage of having to employ a battery of high voltage and capacity because a large drop of voltage through the diode D occurs when the power supply for the motor M is energized from the battery E in series with the diode D.